In recent years, various types of retort rice meals that can be eaten only by heating in hot water or a microwave oven have been commercially available, and many technologies for producing retort rice meals have been suggested (refer to Patent Document 1 to Patent Document 3).
For example, Patent Document 3 describes a retort rice meal producing apparatus which includes a cooking container including heating, cooling, and mixing mechanisms, a retort pouch filling apparatus coupled to the cooking container via a transfer line with a pumping pump and having a filling nozzle for filling a retort pouch with a raw material through the transfer line and a sealer hermetically sealing an opening of the retort pouch filled with the raw material, and a retort sterilizer performing a heat treatment on the hermetically-sealed retort pouch and performing final cooking and sterilization.
In the apparatus disclosed in Patent Document 3, in the cooking container, raw rice cleaned and absorbing moisture is partially added to a cooking liquid containing a viscosity adjusting component, and is kept at a cooking temperature for incomplete cooking. Then, cooling is performed at a temperature equal to or lower than the cooking temperature, and the remaining raw rice is added and mixed, and then obtained mixture is pumped and conveyed via the transfer line to fill a retort pouch from a filling nozzle in the retort pouch filling apparatus and the opening of the retort pouch is hermetically sealed with the sealer. Then, cooking by heat and a sterilizing process are performed in the retort sterilizer. With this, a retort rice meal is produced.
According to the apparatus disclosed in Patent Document 3, in the cooking container, the raw rice is partially added to the cooking liquid for incomplete cooking and then the remaining raw rice is added. Therefore, the ratio of rice grains crushed at the time of pumping and transferring the mixture to break the shape is decreased, and degradation in eating texture and flavor can be prevented.
Also, according to the apparatus disclosed in Patent Document 3, in the cooking container, a process of cooling the cooking liquid after partially adding the raw rice for incomplete cooking is provided. Therefore, it is possible to prevent excessive progress of alpharization of mainly the remaining raw rice to be added after cooling to cause viscosity which makes it difficult to pump and transfer the mixture though the filling line to the retort pouch.